How about a hunters type quick DM mod? It would be death match with only a few realistic weapons and everyone would have very little health, the levels would be in dark, atmospheric settings, with lots of shadows and hiding places because it would be essential to get the jump on your opponents because of the low health. It could be kind of a homage to Seven or Saw where some psycho has trapped people somewhere and will only let one go, you could start matches with a sawish announcer "It's time to play a game." The weapons would be your basics, pistol, shotgun, SMG, sniper, rifle, maybe an ax, chainsaw, or machete for melee weapon.

Anyone think this sounds cool, it'd be really simple to make too I think.